If this is your first visit, be sure to check out the FAQ by clicking the link above.
You may have to register before you can post: click the register link above to proceed.
To start viewing messages, select the forum that you want to visit from the selection below.

On Sat, 28 Apr 2012 21:11:30 -0700, "Sal" wrote:
20m is especially good. I have a 20m dipole and I answered a CQ from
Eastern Russia (4200+ miles) and Viktor RU0ZM, came right back to me. Then
I noticed I was on tune power, 10W. Great night.

"Sal"

Thanks. I turn on my ancient Icom IC-735, tune around 20 meters and
hear nothing. Transmit and I get infinite VSWR. Ok, something is
wrong. After 15 minutes of juggling coax cables, spinning knobs,
pushing buttons, and head banging, the light comes on in my head.
After a nasty wind storm in January, I a tree had destroyed most of my
antenna farm, which I haven't repaired. Rebuild antennas now added to
the things to do list.

"Jeff Liebermann" wrote in message
...
After a nasty wind storm in January, I a tree had destroyed most of my
antenna farm, which I haven't repaired. Rebuild antennas now added to
the things to do list.

--
Jeff

Luckily,in SoCal we don't contend with that very often -- Santa Ana winds in
the canyons being the occasional exception. I feel for you.

Meanwhile, just hang up any old thing and agitate some 'trons. A 20m dipole
at 15 feet (one end tied off to my chimney and the other end to a branch in
my neighbor's macadamia nut tree) is all I have or apparently need. Yes, 1
KW into a SteppIR on a 50 foot tower is better, but at a cost of several
thousand dollars per S-unit.

Really, it's all good. Maybe you heard my long-ago story about my 20m
first-ever QSO with Hawaii. I got a 5-9 but the antenna was primitive: an
existing 10m vertical dipole, with one end clipped to an extension ladder
laying on the ground. True.

On Sun, 29 Apr 2012 12:13:28 -0700, "Sal" wrote:
Luckily,in SoCal we don't contend with that very often -- Santa Ana winds in
the canyons being the occasional exception. I feel for you.

The winds wasn't that bad. I live in a redwood, fir, oak, and madrone
forest, which blocks most of the wind. The problems are caused by
falling trees and limbs. I have a fair size ding in my car hood, and
had an oak tree land on my flat roof, destroying most of my antennas
and trashing in a skylight. Most of the shock was absorbed by my
neighbors roof.
http://802.11junk.com/jeffl/pics/2011-12-03-Storm/
So much for the idyllic life in the forest.
Meanwhile, just hang up any old thing and agitate some 'trons. A 20m dipole
at 15 feet (one end tied off to my chimney and the other end to a branch in
my neighbor's macadamia nut tree) is all I have or apparently need. Yes, 1
KW into a SteppIR on a 50 foot tower is better, but at a cost of several
thousand dollars per S-unit.

There's no way I can rotate a horizontal antenna without hitting a
tree or the hillside behind my house. A tower might help, if it were
200ft high, and the swaying trees won't hit the antenna. I'm stuck
with using wire antennas and verticals.
Really, it's all good. Maybe you heard my long-ago story about my 20m
first-ever QSO with Hawaii. I got a 5-9 but the antenna was primitive: an
existing 10m vertical dipole, with one end clipped to an extension ladder
laying on the ground. True.

Yep, RF is magic. I managed to make a QSO into a Heathkit Cantenna,
but that's about the limits of my non-traditional antenna experiments.
One of these days, I'm going to build an NEC2 model of an aluminum
ladder and see what can be done to use it on VHF or UHF.

So, I climbed up on my roof with a balun and some wire, intending to
make a dipole. Normally, this is a trivial exercise. However,
there's a problem. All the labels have peeled off my multitude of
coax cables. The labels were UV proof but apparently not water proof.
Almost all of my coax cables came off the same roll of RG6a/u and look
identical. This is going to be a problem.

I did manage to find all the parts to a Radio Shock discone antenna,
which is now simulating a wet noodle on top of a 10ft 3/4" PVC pipe.
That's because I can't find a single 10ft mast section that doesn't
have a fatal dent or bend.

The 12ft(?) long VHF/UHF Comet fiberglass antenna survived the tree
fall, but will need to come down for some cleaning. The outside is
covered with green slime. Experience has shown that when the outside
is covered with green slime, so is the inside.

On Sat, 28 Apr 2012 21:11:30 -0700, Sal wrote:
20m is especially good. I have a 20m dipole and I answered a CQ from
Eastern Russia (4200+ miles) and Viktor RU0ZM, came right back to me.
Then I noticed I was on tune power, 10W. Great night.

"Sal"

20m was good yesterday as well, I made several European contacts in just
a few minutes on PSK31 (from 4 land).

I did manage to find all the parts to a Radio Shock discone antenna,
which is now simulating a wet noodle on top of a 10ft 3/4" PVC pipe.
That's because I can't find a single 10ft mast section that doesn't
have a fatal dent or bend.

The 12ft(?) long VHF/UHF Comet fiberglass antenna survived the tree
fall, but will need to come down for some cleaning. The outside is
covered with green slime. Experience has shown that when the outside
is covered with green slime, so is the inside.

Maybe I should give up for the day, and just clean up the workbench.

Scale back a little....
I put up a fan inverted -V cut for 80-40-30 a while back just to test.
I use a tuner, as long as the transmitter likes it, I like it.
I hardly ever use 80m, no particular reason, I just don't.
The ends droop to whatever was convenient. I did not bother to
consider anything permanent. Most of the ends are secured at the
perimeter of the yard via nylon braided line attached to military
surplus fiber glass mast sections leaning into convenient trees. I
only worried about keeping the ends high enough to avoid contact with
people, tractors and deer in the yard.

It seems to work well on all bands I have tried. Although I prefer my
manual MFJ tuner, the internal tuner in my TenTec Jupiter seems to do
OK. I am not a contester, a DX hound or a perfectionist but I do like
to spend a little time on the air.

I would make up a coax balun of about 8 turns of coax on a milk jug
with connectors appropriate to the roof connections. The Dollar Store
here sells black vinyl tape for about $1 for two rolls so wrap the
balun up well enough to not become a future problem. Pick any cable
handy on the roof, assuming that they all go to the shack. When you
get to the shack, use the cable that has signals on it.

I don't know which direction is favored on any band nor do I really
have any idea which elements are active under any given circumstance.

It will keep you on the air and give you time to decide where you want
to go from here with out undue pressure!
John Ferrell W8CCW

On Mon, 30 Apr 2012 12:18:29 -0400, John Ferrell
wrote:
I put up a fan inverted -V cut for 80-40-30 a while back just to test.
I use a tuner, as long as the transmitter likes it, I like it.

If it's anywhere near a 1/2 wave dipole, a fan dipole shouldn't need a
tuner. I've built two fan dipoles over the years. Since everything
affects everything else, I spent far too much time adjusting the wire
lengths. I eventually settled on a trapped dipole, which was easier
and worked the first time. Either antenna would work for me except
for the length. I don't have the room for a proper 80 meter dipole.
For the immediate problem, I'll be happy if I can get on 20 meters
(PSK31) and 10 meters (radio club net).
It seems to work well on all bands I have tried. Although I prefer my
manual MFJ tuner, the internal tuner in my TenTec Jupiter seems to do
OK.

Antenna tuners can be quite lossy. Have fun with this Java app:
http://fermi.la.asu.edu/w9cf/tuner/tuner.html

Do you have a field strength meter? Find a location in the pattern
and as far away as practical. View the meter from your operating
position using binoculars or a telescope. Try your fan dipole
directly to the 50 ohm output of your transmitter. Hopefully, the
VSWR will be less than what it takes to trip the VSWR protection
circuitry. Now, install the antenna tuner and try again, keeping the
RF power at the same level. If you have problems leveling the RF
power, use an AC powermeter, such as a Kill-a-Watt, to measure the AC
input power consumption. When I did the same test, the antenna tuner
always had noticeably less TX signal strength.
I am not a contester, a DX hound or a perfectionist but I do like
to spend a little time on the air.

I spend more time inside the radios than in front of them.
It will keep you on the air and give you time to decide where you want
to go from here with out undue pressure!

The answer for me was supplied by outside influences. A mess of work
arrived at my shop, so I'll be too busy to do antennas for a while.

Jeff Liebermann wrote:
On Mon, 30 Apr 2012 12:18:29 -0400, John Ferrell
wrote:
I put up a fan inverted -V cut for 80-40-30 a while back just to test.
I use a tuner, as long as the transmitter likes it, I like it.

If it's anywhere near a 1/2 wave dipole, a fan dipole shouldn't need a
tuner. I've built two fan dipoles over the years. Since everything
affects everything else, I spent far too much time adjusting the wire
lengths. I eventually settled on a trapped dipole, which was easier
and worked the first time. Either antenna would work for me except
for the length. I don't have the room for a proper 80 meter dipole.
For the immediate problem, I'll be happy if I can get on 20 meters
(PSK31) and 10 meters (radio club net).

FYI I spent an afternoon with EZNEC exploring fan dipoles.

What I found was the farther apart the wires, the less the interaction,
which is what one would expect from common sense.

From my limited runs it appears that somewhere around 20 degrees is about
where the minimum separation needs to be for practical length adjustments.

At angles less than that be prepared to spend a lot of time pruning.

It doesn't matter if the wires are separated vertically or horizontally
other than horizontal separatation means you need lots of support points.

If the bands are too close together, i.e. 20-17, 17-15, 12-10, you can
never get both bands to "work", i.e. a decent match.

That appears to be also true for trap antennas from some limited EZNEC
modeling.

Of course, there is always the alternative of throwing technology and
money at the problem and just put up whatever wire you can and put an
autotuner up.

On Mon, 30 Apr 2012 12:18:29 -0400, John Ferrell
wrote:
I put up a fan inverted -V cut for 80-40-30 a while back just to test.
I use a tuner, as long as the transmitter likes it, I like it.

If it's anywhere near a 1/2 wave dipole, a fan dipole shouldn't need a
tuner. I've built two fan dipoles over the years. Since everything
affects everything else, I spent far too much time adjusting the wire
lengths. I eventually settled on a trapped dipole, which was easier
and worked the first time. Either antenna would work for me except
for the length. I don't have the room for a proper 80 meter dipole.
For the immediate problem, I'll be happy if I can get on 20 meters
(PSK31) and 10 meters (radio club net).
snip

I have antenna challenged yard, with no available supports for horizontals.
So I've been experimenting with vertical radiators mounted on a 12 by 30
foot metal patio cover.

Initially, I used a CB whip, fed with RG-58 to a tuner in the shack, quite
successfully on 24 and 28 MHz. After a few more tests, (and more tests are
planned) I settled on a 14 foot radiator that works well on 20-10 meters.
It did a good job on all those bands during the recent DX contests, but
obviously won't bust a full fledged pileup without some operational cunning.

The antenna is fed with 25 feet of RG-8 to an RF ammeter in the shack and on
to a tuner. The ammeter is used to get the most current with various tuner
settings/configurations, but without changing anything from the ammeter to
the antenna.

So, a tuner in the shack feeding a single dipole might fit your band
coverage and real estate requirements. Play around a bit with EZNEC and try
a few things.